1. Field of the Invention
Apparatuses consistent with the present invention generally relate to an antenna applied to a slide type mobile communication terminal. More particularly, the present invention relates to an antenna applied to a slide type mobile communication terminal for implementing directionality while a type of the antenna is retained.
2. Description of the Related Art
An antenna operates to convert an electrical signal and an electromagnetic signal. The antenna serves to receive a radio frequency (RF) signal at a mobile communication terminal or transmit an internal signal over the air.
Characteristics of the antenna include the radiation pattern, voltage standing wave ratio (VSWR), efficiency, and gain. Particularly, an antenna applied to a mobile communication terminal requires omni-directionality, high efficiency, and low VSWR.
The antennas applied to mobile communication terminals can be classified largely into an internal antenna and an external antennal. Examples of the internal antenna include a ceramic chip antenna and an inverted-F antenna. Examples of the external antenna include a helical antenna and a monopole antenna.
Most mobile communication terminals including mobile phones employ antennas capable of implementing the omni-directional radiant gain pattern because it is impossible to know in which direction radio waves come from.
Recently, mobile communication terminals are applied to not only mobile communications but also short range communications such as radio frequency identification (RFID) systems. In response to this, antennas for short range communications should implement the radiation pattern with the directionality and extend the reading range of RFID tags.
By way of example of solutions for increasing the gain of the antenna with the implementation of the directional radiation pattern, an antenna fixed to and extending along a cover beyond a housing of a portable radiotelephone is disclosed in WO 9809414.
To maximize characteristics of a dipole antenna, the total length of the antenna should be half wavelength. Yet, the length of typical mobile communication terminals does not meet this requirement. To this end, the antenna is constructed to satisfy the half wavelength in length by forming the antenna along the cover and the housing.
In the disclosed literature, since the antenna is disposed along the cover and the housing of the mobile communication terminal, when the cover slides up, the extension of the antenna enables communications. However, to fix the antenna as above, a considerable space is needed in the mobile communication terminal. Accordingly, there is a problem in that the total length of the antenna may enlarge the size of the mobile communication terminal.
To increase the gain of the antenna with the implementation of the directional radiation pattern, another antenna, disclosed in U.S. Pat. No. 5,966,099, includes a reflector disposed on the outside of the internal monopole antenna.
The antenna having the reflector can increase the gain of the antenna by realizing the directional gain pattern, but may occupy a considerable space in the mobile communication terminal to keep an interval between the monopole antenna and the reflector.